Conventional toothbrushes, including both manual and power-driven embodiments, attempt to produce the desired cleansing effect by scrubbing the surfaces of the teeth to remove dental plaque. Flossing is typically recommended in addition to brushing to reach those tooth areas which cannot be reached by a brush.
However, it is well-known that flossing is inconvenient and difficult to perform. Consequently, only about 15% of the population practice flossing regularly. In addition, conventional brushing action, particularly over an extended period of time, can result in undesirable wear on teeth surfaces.
In order to improve on the brushing/flossing combination, a number of different technical approaches have been used, with varying success. A first category or group of devices involves the water jet phenomenon. Representative examples of patents in this group include U.S. Pat. No. 3,227,158, to Moret, and U.S. Pat. No. 3,522,801 to Robinson. Typically, these devices use a pulsating, highly directed stream of fluid to remove material from around the teeth. However, these devices do have significant disadvantages, including a requirement of relatively high water pressure. Generally, these devices are not very effective in removing plaque. In addition, bacteremia sometimes results from use of these devices. Further, a water jet device is powered by line voltage (not batteries), and typically requires a significant amount of shelf space.
A second group of devices includes those in which a brush is vibrated at an ultrasonic frequency rate to produce a cavitation effect which in turn results in the desired cleansing. U.S. Pat. No. 3,335,443 to Parisi and U.S. Pat. No. 3,809,977 to Balamuth are examples of such devices. The primary difficulty with such devices is the requirement of providing energy through the bristles at ultrasonic frequencies, which are substantially higher than the resonant frequency of the bristles, resulting in very low efficiency of energy transfer to the tips of the applicator. Safety problems may also be significant with such devices, due to the application of ultrasonic energy to tissue.
In still another group are devices which operate at low sonic frequencies but which also allegedly produce a cavitation effect. U.S. Pat. Nos. 3,535,726 and 3,676,218, both to Sawyer, are representative of this group. It is questionable, however, that a vaporous cavitation effect is actually produced by these devices, particularly for those which are hand held and indicated to be powered by batteries.
Lastly, some devices operate in the low audio frequency range (200-500 Hz), and produce what is characterized as mild cavitation, combining that effect with conventional bristle scrubbing action to achieve cleansing. An example of such a device is shown in U.S. Pat. No. 4,787,747 to Martin et al. This device is effective at least to some extent in disrupting plaque colonies. However, the "cavitation" produced by this device, which in fact is not vaporous cavitation (vaporous cavitation being often referred to as "true" cavitation) does not extend beyond the tips of the bristles, and therefore the device is not particularly effective in the inter-dental and subgingival areas of the teeth where enhanced cleansing is needed.
Accordingly, there remains a need for a toothbrush device which has a significant cleaning effect beyond the tips of the bristles, reaching important areas such as the interdental and subgingival regions, yet is safe as well as convenient to use.